1. Field of the Invention
The present disclosure relates to a method and apparatus for updating a sleep identifier in a broadband wireless communication system, and more particularly, to a method and apparatus for updating a sleep identifier of the sleep mode terminal when a traffic indication message containing an updated sleep identifier has not been received.
2. Description of the Related Art
The issue of power consumption in a terminal may be a very important factor in a broadband wireless mobile communication system compared to other systems because the mobility of a terminal should be taken into consideration. A sleep mode operation between a terminal and a base station has been proposed as one of such methods for minimizing power consumption in a terminal.
In a sleep mode operation, a terminal requests to enter into a sleep mode if there exists no more traffic to be transmitted and/or received to and/or from a base station while performing a communication with the base station in an active mode, and receives a response to that request from the base station to change the state thereof to a sleep mode.
The terminal that has entered into a sleep mode state receives a message indicating whether there exists a traffic transferred from the base station during a sleep listening window, and determines that there exists no data traffic transmitted to a downlink when negative indication indicating that there exists no traffic is received.
Furthermore, if positive indication is received from the base station during the listening window, then the terminal determines that there exists data traffic transferred to a downlink, and initializes the current sleep cycle. At this time, the type of data traffic that can be received by a terminal may be a real time or non-real time service, and it has a feature that packet data transmitted and/or received to and/or from the terminal will have non-periodicity if a non-real time service is received such as short message, and packet data transmitted and/or received to and/or from the terminal will have periodicity if a real time service is received such as VoIP (Voice on IP).
FIG. 1 is a flow chart sequentially illustrating a typical sleep mode operation.
A terminal performs communication with a base station in a normal or active mode, and transmits a sleep-request (SLP-REQ) message for entering into a sleep mode to the base station if there exists no more traffic to be transmitted and/or received to and/or from the base station (S101).
The base station receives the SLP-REQ message from the terminal, transmits a sleep-response (SLP-RSP) message to the terminal in response to the SLP-REQ message (S102).
The SLP-RSP message may include a sleep mode parameter for operating the sleep mode of a terminal, such as a sleep cycle, a listening window, and the like. The terms, “listening section” and “sleep interval”, used below shall have the same meaning as “listening window” and “sleep window”, respectively.
According to circumstances, even without the sleep-request message of the terminal (S101), the base station may directly transmit an unsolicited SLP-RSP message to the terminal, thereby giving a command to allow the terminal to enter into a sleep mode.
The terminal that has received a SLP-RSP message from the base station changes the state to a sleep mode by referring to a sleep operating parameter to perform a sleep mode operation.
The sleep mode may include a sleep window (SW) incapable of receiving data and a listening window (LW) capable of receiving data.
In the sleep mode, the base station transmits a traffic-indication (TRF-IND) message to the terminal to indicate whether or not there exists traffic to be transferred to the terminal during a listening window (S103).
The TRF-IND message indicating the existence or non-existence of the traffic is set to positive indication if there exists traffic, but set to negative indication if there exists no traffic.
If a positive TRF-IND message is received, then the terminal transmits or receives the generated data traffic during the listening window (S104), and enters into the sleep window (SW) to perform a sleep mode operation.